Added surface area calculation for pyramid

src/main/java/com/thealgorithms/maths/Area.java

@@ -35,6 +35,26 @@ public static double surfaceAreaCube(final double sideLength) {
         return 6 * sideLength * sideLength;
     }
 
+    /**
+    * Calculate the surface area of a pyramid with a square base.
+    *
+    * @param sideLength side length of the square base
+    * @param slantHeight slant height of the pyramid
+    * @return surface area of the given pyramid
+    */
+    public static double surfaceAreaPyramid(final double sideLength, final double slantHeight) {
+        if (sideLength <= 0) {
+            throw new IllegalArgumentException("Must be a positive sideLength");
+        }
+        if (slantHeight <= 0) {
+            throw new IllegalArgumentException("Must be a positive slantHeight");
+        }
+        double baseArea = sideLength * sideLength;
+        double lateralSurfaceArea = 2 * sideLength * slantHeight;
+        return baseArea + lateralSurfaceArea;
+    }
+
+
     /**
      * Calculate the surface area of a sphere.
      *